1. Field of the Invention
This invention pertains generally to the grinding and drying of material, such as coal, and particularly to apparatus for working material and segregating the worked material into different classifications according to specific gravity characteristics.
2. Description of the Prior Art
There are a number of types of apparatus useful for segregating grindable materials so that coarse and fine constituents can be collected at different outlets of the apparatus according to the purpose of such segregation. One such apparatus is shown in the prior patent of Williams U.S. Pat. No. 3,794,251, issued on Feb. 26, 1974. Another related apparatus is shown in Williams U.S. Pat. No. 3,981,454, issued Sept. 21, 1976 wherein segregation of material is effected by use of an air column so that advantage is taken of specific gravity characteristics of the material being processed. A further prior art patent is Williams U.S. Pat. No. 3,844,491, issued Oct. 29, 1974, wherein segregation has involved magnetic as well as specific gravity characteristics.